The Molecular Embryology and Pathology Core will provide Projects 1,2,3,4 and 5 with routine and specialized molecular embryology and pathology facilities and services. This Core is planned to provide efficient and cost effective services. The projects share needs for embryonic, lung explant culture, in situ hybridization, immuno- histochemistry, microscopic imaging, photography, and stereology including computer three-dimensional reconstruction and morphometry as well as electron microscopy. This Core will provide routine and high quality organ explant culture services, and will provide centralized and cost effective histolog and photomicroscopy services as well as stereology and morphometry facilities.